1. Field of the Invention
This invention relates to an electrical connector for electrically connecting electrical units, an electrical device, and a production method for producing an electrical device, in particular to a three-dimensional electrical device taking a rectangular parallelepipedic shape and provided at specified positions with electrical function elements such as stress detecting elements represented by distortion gauges and various integrated circuits.
2. Description of the Related Art
Japanese Patent No. 2736395 shows a stress detecting sensor which includes an electrical three-dimensional unit having a rectangular parallelepipedic shape and at least the outer surface thereof made of an electrically nonconductive material, and distortion gauges made of metal resistor foils or a semiconductor elements and formed on the respective surfaces of the electrical three-dimensional unit. Such a stress detecting sensor is embedded in a structure for which an internal stress is to be measured such as an axle of a vehicle. Distortion signals outputted from signal lines drawn out from the respective distortion gauges are calculated by a specified arithmetic circuit, whereby a stress occurred inside the structure can be precisely detected. By using such a stress detecting sensor, detection precision is remarkably improved as compared to a conventional stress detecting method according to which distortion gauges are adhered to outer surfaces of the structure. Thus, attention is paid to the application of such a stress detecting sensor, for example, to an axle of a vehicle since a very precise ABS (anti-braking system) control can be realized.
Such a stress detecting sensor in which the distortion gauges are attached to the respective surfaces of the electrical three-dimensional unit can fully display its function even when only one sensor is provided. However, if a plurality of stress detecting sensors are linearly connected into a long line or two-dimensionally connected to span in a plane or three-dimensionally connected to span in a space, the obtained integrated assembly of the stress detecting sensors has advantages of being able to conform to the shape of a structure to be measured and suitably detect an internal stress and geometrically progressively improving detection precision. As an example, an assembly of stress detecting sensors is shown in Japanese Patent No. 3131642.
Electrical connection of three-dimensional detecting sensors into an integrated assembly has been conventionally made by forming land portions of wiring patterns on the respective surfaces at respective corner portions or ridge portions of each three-dimensional detecting sensor, and placing connection pads made of, e.g., gold on these land portions, subsequently applying a high-temperature heating treatment while the connection pads of the three-dimensional detecting sensors are held in contact with each other to thereby connect the connection pads.
However, since a plurality of stress detecting sensors held in contact with each other are heated at high temperatures according to the conventional method, there are problems that voids or holes are formed in the synthetic resin material forming the body of the three-dimensional detecting sensor due to the fact that gold forming the connection pads and aluminum forming the land portions come into a mixture or an alloy and the alloy then grows, and the heated three-dimensional detecting sensor made of the synthetic resin is consequently deteriorated due to heat corrosion, and the electrical function elements mounted on the three-dimensional detecting sensor are adversely affected.